NAC445A.9666. Effluent absorption system.

     1. The effluent from a septic tank or other treatment unit must be disposed of through a soil absorption trench or other effluent absorption system pursuant to NAC 445A.9666 to 445A.969, inclusive, and approved by the Division or other administrative authority.

     2. The size and type of effluent absorption system required for an on-site sewage disposal system must be determined according to:

     (a) The requirements for the sizing of the septic tank as determined pursuant to NAC 445A.9656;

     (b) The long-term acceptance rate calculations made pursuant to NAC 445A.9674; and

     (c) The results of percolation tests or other soils analyses conducted pursuant to NAC 445A.9668 or 445A.967. The slowest percolation rate generated by the percolation tests or other soils analysis must be used to determine the required size of the effluent absorption area.

     3. Soils used in an effluent absorption system must have a percolation rate that is 120 minutes per inch or less without interference from groundwater or impervious strata below the level of the effluent absorption system.

     4. If the percolation test or other soils analysis yields a percolation rate of less than 5 minutes per inch, the Division or other administrative authority may require that:

     (a) The effluent absorption area be specially designed by the design engineer to slow the effluent for proper treatment; and

     (b) The required setbacks from any well or watercourses be increased.

     5. The treatment unit and the effluent absorption system must be separated by at least 5 feet, and the solid watertight pipe that connects the treatment unit and the effluent absorption system must be placed on undisturbed soil.

     6. Except as otherwise provided in this section, the distribution pipes must:

     (a) Be of equivalent length unless otherwise authorized by the Division or other administrative authority.

     (b) Consist of perforated drain pipe made of polyvinylchloride unless otherwise approved by the Division or other administrative authority.

     (c) Be laid in such a manner that the bottom of the pipe is not less than 12 inches or more than 48 inches below the ground surface.

     (d) Be laid in continuous straight or curved lines with a slope of not less than 2 inches or more than 4 inches per 100 feet of pipe.

     (e) Be laid in such a manner that perforations are facing down.

     (f) Be equipped with end caps or vented to the surface at the end of each pipe.

     (g) Not exceed 110 feet in length unless a longer length is justified by the design engineer and approved by the Division or other administrative authority.

     7. The effluent absorption area, including the site of the installed effluent absorption system and the backup area required pursuant to subsection 2 of NAC 445A.9602, must not be the site of activity that is likely, as determined by the Division or other administrative authority, to affect adversely the soil or the operation of the on-site sewage disposal system, which may include, without limitation, vehicular traffic, filling, cutting or other soil modification, or covering the area with a permanent structure, asphalt, concrete or a similar substance.

     8. Monitoring ports must be located, at a minimum, in the center and at each end of the effluent absorption area. Additional monitoring ports may be included at representative points in the absorption area, as determined by the design engineer, to allow adequate assessment of the operating conditions and to measure any anticipated liquids at critical depths within the absorption bed or trench. The monitoring ports must be a minimum of 4 inches in diameter.

     9. At least one down-gradient monitoring well, to sample groundwater quality in the area of the absorption area, may be required by the Division or other administrative authority, with additional wells required depending on the topography of the site and the size of the on-site sewage disposal system. Each well must extend to sufficient depths to sample seasonal fluctuations of the unconfined water table. The wells must conform to the guidelines for the design of groundwater monitoring wells established by the Division.

     10. A distribution box must be used in an absorption system with more than one distribution line unless a pressure distribution system is used. Each distribution line must be separately connected to the distribution box. The number of outlets of a distribution box must be equal to or more than the number of distribution lines to be used in the absorption area. The inverts of all outlet lines from a common distribution box must be set at the same level and must be above the level of the bottom of the distribution box. The inverts of all inlet lines to a common distribution box must be at least 1 inch higher than the level of the invert of the outlet lines from the same distribution box. A distribution box must:

     (a) Be watertight and constructed of durable material that is resistant to corrosion, including, without limitation, concrete, fiberglass, polyethylene or any other material approved by the Division or other administrative authority.

     (b) Be placed so that the box is level and must be maintained in that manner.

     (c) Be designed to ensure equal flow.

     (d) Have a cover that is made of the same material as the distribution box.

     (e) Be installed on:

          (1) Aggregate;

          (2) A level concrete slab which is at least 6 inches in depth and which extends 6 inches or more beyond the perimeter of the distribution box; or

          (3) Undisturbed soil.

     11. Except as otherwise provided in this section, aggregate used in the effluent absorption area of an on-site sewage disposal system must have a minimum size of 3/4 inch and a maximum size of 2 1/2 inches. The aggregate must be durable and inert so that it will maintain its integrity and not collapse or disintegrate with time and must not be detrimental to the performance of the system.

     12. Except as otherwise provided in this section, the bottom of the absorption system disposal field must be at least 4 feet above the level of the seasonal high groundwater of the site.

     (Added to NAC by Environmental Comm’n by R194-07, eff. 8-26-2008)